Foam generating apparatus



April 8, 1958 H. G. FREEMAN 2,829,874 FOAM GENERATING APPARATUS FiledMay 4, 1954 INVI'L'NTOR. HOWARD G. FREEMAN BY 1 ATTORNEYS 2,829,874 FOAMGENERATING APPARATUS Application May 4, 1954, Serial No. 447,848 (Filedunder Rule 47 1) and as U. s. c. 118) 3 Claims. 01. 261-76) The presentinvention relates to the generation of fire fighting foam, and moreparticularly to a nozzle for producing a stream of finely divided foam.

The present invention constitutes an improvement in the foam generatingapparatus shown in the Freeman and Hencinski Patent No. 2,492,037,issued December 20, 1949. As pointed out in that patent, it is necessaryto use a nozzle having a number ducing fire fighting foarm for thepurpose of smothering a fire through the exclusion of air. Thefoam isformed of water and a foaming agent, and should be of a'very finelydivided structure characterized by a multitude'of fine bubbles and arelatively small water content. In view of the fact that foam isfrequently used in fighting gasoline and oil fires, it is necessary thatthe stream of foam be projected well forwardly of the nozzle." Thenozzle described in the above patent achieves the desired result by acombination of fog head with an aspirating hood and a screen which "isplacedin thefront of this nozzle. Air is aspirated through the hood, andthe screen acts'to promote contact between the finely divided dropletsand foam-forming agent.

It is the principal object of the present invention to provideimprovements in the foam producing nozzle of my prior patent,particularly with a view to producing a fine and tenacious foam, with anadequate range and angle of dispersion.

With this object in view, the present invention comprises thefoam-generating apparatus hereinafter described and defined in theappended claims, particularly in the combination of the nozzle andaspirating hood with a multiple screen assembly.

The single figure of the drawing is a section of an illustrativeembodiment of this invention.

The nozzle head 10 by which the spray of droplets is generated ismounted within the nozzle body at the end of the inlet section 12. Theinlet is threaded to permit attachment to a supply hose by which thepreviously mixed solution of foam-forming agent and water is suppliedunder pressure.

The nozzle head is provided with a pair of passages 16 inclined to thenozzle surface where they combine to form the spray generating orifice14. The center lines of this pair of passages preferably intersectsubstantially in the nozzle surface, as described in my Patent No.2,302,021, issued November 17, 1942. At liquid pressures greater thanthe order of 30 pounds per square inch, a fan shaped spray or fog ofvery fine droplets or mist is discharged from the orifice. For somepurposes, a relatively wide discharge pattern is desirable, in whichcase the nozzle head may have a number of pairs of intersectiingorifices arranged to provide diverging sprays. However, because of thediverging effect of the screen assembly which is attached at the end ofthe hood in this invention, a single pair of passages forming oneorifice provides an adequately diverging foam spray pattern.

2,829,874 PatentedApr. 8, 195$ The high velocity spray has, by reason ofthe large amount of elfective area provided by the multitude of finedroplets, a very substantial aspirating effect. This causes anappreciable amount of air to be drawn into and swept along with thespray of mist. In general, for the greatest amount of foam withoutsacrifice of foam quality, the optimum ratio of volume of air to volumeof liquid is somewhere between 5 to 1 and 8 to 1. Introduction of air insubstantially the optimum ratio may be efiectively accomplished by theprovision of a hood through which the spray is projected. This hood maybe formed by an enlarged diverging funnel of such dimensions as not torestrict the spray pattern provided by the orifice arrangement in thenozzle head. To admit air to the hood, openings 22 are provided, throughwhich air is drawn by the sweeping action of the droplets moving at highvelocity toward the discharge.

of characteristics in proa high velocity water The parts thus fardescribed are in general similar to corresponding parts in theabove-mentioned Freeman and Hencinski patent. To complete theentrainment of air within the droplets of water and foam solution, themixture of air and spray is caused to impinge on and be projectedthrough two screens 27 and 29 arranged to form what may be termed ascreen lens, carried at the end of the aspirating hood. The spacingbetween the screens and the nozzle head such as to allow thoroughintermingling of air and droplets before the mixture reaches the screen.

The screen lens preferably comprises a substantially fiat screen 27which first intersects the spray and a second screen in the form of adome 29 which forms the outerface of the lens. The edges of thesescreens are carried in adjacent relationship in a hemispherical channelformed on the end of the aspirating hood. The mesh of these screensvaries between 3 and 10 to the inch, and both are conveniently, but notnecessarily, of the same mesh. The screens are contiguous at theirmargins and are secured within a lip 25 of the hood.

The effect of this screen lens is not only to produce a dense foamhaving a large number of finer bubbles, but also to spread the foam in adiverging stream. The flat screen tends to narrow the stream, but theconvex screen causes some divergence of the pattern.

It has been found that the screen separation formed in this constructionis preferably not less than A" and not more than 1 /2" in the regionintersecting the droplet stream. This range of separation between thetwo screens is desirable for optimum performance both in creating foamand in maintaining a broad pattern of flow from the nozzle.

A nozzle embodying these features of construction and operation providesa broadly diverging discharge pattern which enables a substantial areato be blanketed with foam and which also affords substantial protectionto the operator from the heat of the flames. Furthermore, the improvedmixing action of the screen lens disclosed herein permits the nozzle tomix a maximum volume of air for each gallon of liquid discharged throughthe nozzle head. The large volume of high quality foam which is providedin this construction is particularly significant in the case of portableequipment where water capacity may be limited. In the case of a truckcarrying 1000 gallons of water, for example, the use of this foam nozzlein conjunction with the addition of a relatively small quantity offoam-forming agent, makes available a supply of as much as 8,000 gallonsof smothering foam.

Having thus described the invention, I claim:

1. A nozzle for generating a foam for fire fighting having incombination a body member having an inlet end, an outlet end, wallsdefining a converging fluid passage towards said outlet end, and saidbody member of foam-forming agent and water having a threaded portionon'the inlet end whereby said body'rnember may be connected toa sourceof a solution under pressure, a head membermounted in the outlet end ofsaid body-having a plurality of separate fluid passages all convergingat'the outlet end'of said body member, a hood member mounted on theoutlet 'end of said' body member having walls defining a first divergingfiuid passage, said 'walls having a plurality of openings formed'thereinwhereby air may be drawn into said first diverging fluidpassage, a firstscreen member mounted in said hood member having-a substantially planarconfiguration, and a second screen memberm'ounted in said hood memberhaving a'substantially convex configuration, whereby said screen membersdefine a seconddiverging fluid passage.

2. A nozzle for "generatingfoam 'for fire fighting having in combinationa' body member having an inlet end, an outlet end, walls defining aconvergingfiuid passage towards said outlet end, and'sa'idbody' memberhaving a threaded portion on the'inlet end"whereby'fsaid body member maybe connected'to a source of a'sblution of foam-forming agent and'waterunder pressure, a head member mounted in the outlet end of said bodyhaving a plurality of separate fluid passages all convergingatthe outletend of said body member, a hood member mounted on theoutlet endof'saidb'ody" member having walls defining afirst diverging fluidpassage of substantially greater cross-section than 'said convergingtfirid "passages, said walls havinga plurality of aspirati'nlgports insaid hood member w'allsformed' therein whereby air may be drawn intosaid diverging fiuidpassagefaninner screen member'and an outerscreenmemberhavingfcontiguous edges carriedby'the end ofsaidhood"'men'1ber, and spaced from the outlet end of said body member,said inner's'creen member having a substantially planar configuration,and said outer screen member havinga" substantially convexconfiguration, said screen "members having a substantial separationforming a lens-like assem- "bly"whereby {substantially diverging" foamdistribution pattern is produced.

3. A nozzle for generating foam for fire fighting having in combinationa-"body member having an inlet end, an outlet end, walls d"firiing aconverging fluid passage towards's'aid outlet end, and said body memberhaving a threaded portion on the inlet end whereby saidbodyrnember'may'be' connected to a source of a solution of foam-forminagent 'and 'waterunder pressure, a head member mounted in the outlet endof said body having a pluralitybf separate fluid passages all convergingat the outlet end ofsaid body member, a hood member mounted on theoutletend of said" body member having walls defining a first divergingfluidpassage-of substantially greater cross-section than said convergingfluid passages, said walls having a plurality of aspirating ports insaid hood member walls formed thereinwherebyair may"be drawn into saiddiverging fluid-passage aninner screen member and an outer screenmemberhaving-contiguous edges carried by the end of said hood member,and spaced from: the outlet end of said bodymember, said inner screenmember having a substantially :planar 7 configuration andsaid outerscreen member having a substantially convex configuration, said screenmembers'having aiseparation of between A" and 1 /z"'in-the path of saidfirst diverging fluidpassage forming a lens-like assembly'whereby asubstantially diverging foam-distribution pattern is produced.

References Cited in the file'of this patent UNITED STATES PATENTS IHolden ..i. June 23, 1953

